Method for producing a liquid electrolyte battery

ABSTRACT

The invention relates to a method for making an electrolytic battery which is preferably used in movable facilities such as cars, boats and planes. The method comprises the following steps: Inserting of intermixing plates  5   a ′ into the battery case  1 , one each at two sides thereof which are opposite to each other, inserting of the set of electrodes  2  between the two intermixing plates  5   a ′ positioned in the battery case  1  and connecting of the two intermixing plates  5   a ′ straightened out vertically with the bridging plate  5   b ′ comprising a drain surface, which is slightly inclined towards the center thereof, and an opening provided approximately in the center thereof to enable electrolyte to flow back into the batter case.

The invention relates to a method for making an electrolytic batterywhich is preferably used in movable facilities such as cars, boats andplanes.

The endeavor of car industry for weight-saving constructions alsoincludes a reduction of battery weight. At the same time, there is thedemand for increasing the battery performance in order to provide enoughenergy for starting a vehicle and for operating additional units such aselectrical window lifters, seat-adjusting devices and seat heaters.Furthermore, there is the demand for keeping the performance of abattery at an almost constant high level during the lifetime thereof.

Several measures to increase the performance of such a conventionallead-acid battery are known from prior art. The performance of batteryis understood to be the capability thereof to supply and receive acurrent.

A great problem occurring with lead-acid batteries is to utilize thetotal surfaces of electrodes almost completely. When the acidconcentration in an area of the surface of electrode is too high, theelectrodes are subjected to corrosion and are decomposed. When the acidconcentration is too low, there is a lack of electrolytic properties sothat a battery does not work reliably. Due to certain effects known fromprior art, the density of acid is uneven within a battery. In order toeliminate this deficiency, devices for intermixing the electrolyte weredeveloped. Such devices also prevent that depositions affecting thefunction and life of a battery are formed.

Document DE U 9114909 discloses an accumulator battery, the electrolyteof which being circulated by introducing pressurized gas into it.However, this method of circulation is suited for car batteriesrestrictedly only, because the circulation device has a very complexstructure and a pressure-gas source is required. Devices for intermixingthe electrolyte, which are called hydrostatic pumps, are known fromprior art. In the following, the function of such devices is described.When a vehicle is moved at an even speed, i.e., when it is whetheraccelerated nor decelerated, the surface of liquid electrolyte in thebattery is smooth and leveled. When a car is accelerated or decelerated,the electrolyte is pushed back and forth, due to its mass moment ofinertia. Flows of electrolyte arising from such movements are guidedthrough channels and barriers so that an intermixing is gained as goodas possible.

This principle representing the closest of prior art is described in thedocuments U.S. Pat. No. 4,963,444, U.S. Pat. No. 5,096,787, U.S. Pat.No. 5,032,476 and the German utility model 297 18004.5, among others.Object of the closest of prior art is an angle-shaped intermixing devicearranged between the electrodes and one of the side walls of a batterycase, as shown in FIG. 1.

Conventionally, when a battery with or without an intermixing device ismanufactured, the first step is to insert the set of electrodes 2 intothe empty case thereof. When a battery is to be equipped with anintermixing device, the set of electrodes has to be positioned exactlyso that the gap between its vertical edge and the side wall of batteryat one side thereof has the same width as that on the opposite side.However, this can be realized under difficult condition only, becausethe massive set of electrodes has to be inserted manually, due to thefact, that using of a robot or a similar handling device would be tooexpensive.

The electrode plates are protected by a foil made of plastic material,which is mechanically very sensitive and hereinafter called electrodebag. Inserting of an angle-shaped mixing plate into the gap between thevertical edge of each of the electrode plates and the side wall at theright side and the left side of battery must be done very carefully toprevent the electrode bags from being damaged. Damaged electrode bagswould lead to a premature breakdown of the respective battery cell andthus, to a reduced capacity of battery.

With the case shown in FIG. 2, the set of electrodes is positioned sothat the gap between the vertical edge of each of the electrode platesand the side wall at the left side of battery is smaller than that atthe right side.

Another disadvantage of the conventional production process isschematically represented in FIG. 3 a. When the set of electrode platesis incorrectly positioned as shown in FIG. 3 a, the flow channel formedbetween the vertical leg of the mixing plate and the side wall at theright side of battery has a smaller depth than that at the left side.However, as the flow channels are optimized with regard to the depth,any change of depth inevitably leads to a reduction of efficiency ofintermixing. With the case shown in FIG. 3 b, the depth of theleft-sided flow channel is the same as that of the right-sided one sothat an effective intermixing takes place, as indicated by arrows.

Still another harmful disadvantage of this production technology is thatany damage of electrode bags can not be found out when the battery isunder final inspection. Therefore, damaging of electrode bags must beprevented unconditionally. On the other hand, this step of assemblingmay not cause higher cost. Therefore, it is necessary to look for asimple, but nevertheless, to a reliable solution. Thus, object of theinvention is to eliminate the deficiency occurring with the prior art.Especially, damaging of electrode bags shall be avoided.

This object is solved by a method for making electrolytic batterieshaving an intermixing device, as defined in claim 1.

This method comprises the following steps:

-   -   Inserting of one intermixing plate each manually at two        predetermined side walls of battery case, which are opposite to        each other, wherein the intermixing plates are inserted slightly        inclined, i.e., with this method, the angle-shaped intermixing        plates according to the prior art are composed of a vertical and        a horizontal portion. Hereinafter, the vertical portion is        called intermixing plate. Dependent on the type of construction        of a battery, the intermixing plates are positioned in the        battery case under an angle of about 10 to 20 degrees.    -   Inserting of the set of electrodes between the two intermixing        plates positioned in the battery case, which thereby are pushed        to a vertical position, i.e., when the set of electrodes is        inserted into the battery case manually, the intermixing plates        are shifted or pushed to the predetermined vertical position. As        the intermixing plates are light and smooth, there is no danger        that the electrode bags are damaged during this procedure. In        addition, when the set of electrodes is inserted manually, it is        shifted to the correct position by the intermixing plates        serving as centering means.    -   Placing a bridging plate horizontally onto the two intermixing        plates straightened out vertically.

These technological steps of making batteries enable advantage to begained as follows.

As the intermixing plates of the divided intermixing device are insertedbefore the set of electrodes is positioned between them, damaging of thesensitive electrode bags can be prevented, largely. This is anauto-centering process, which can further be supported when the batterycase is placed on a conveyor having small rolls.

In addition, with the manufacturing method according to the invention,the electrode plates are exactly positioned by means of the intermixingplates arranged at two sides of the battery case. This is advantageousin that the electric terminals of all of the electrode plates areexactly aligned to each other. Thereafter, the terminals are connectedwith each other by a welding robot so that the battery cells areconnected in series. Up to now, the terminals had to be relatively wideto enable them to be welded together even if they are not alignedexactly. According to the invention, the electrode plates are exactlyaligned to each other so that there are no great tolerances to becompensated and the size of terminals can be reduced without affectingthe accuracy of welding process. Due to the smaller terminals, about 200g and more of lead can be saved per battery.

As soon as the intermixing plates and the electrode plates are insertedand vertically aligned, the bridging plate is placed onto theintermixing plates and connected with them at right angles to form acompact intermixing assembly. When placed onto the intermixing plates,the bridging plate contributes to equalize deformations of battery casecaused with injection molding and to reinforce the battery case as awhole. Compared with the prior art, another advantage of the inventionis that the upper surface of bridging plate serving as drain surface forthe electrolyte is inclined by a predetermined angle from both end sidestowards the center thereof, wherein the inclination is not changed whenthe bridging plate and the cover of battery are mounted and is almostindependent on manufacturing tolerances of battery case so that anoptimum intermixing effect is gained. Below, the production methodaccording to the invention will be described in more detail by means ofthe accompanying drawings.

FIG. 1 is a side view of a lead-acid battery according to the prior art,which is provided with an angle-shaped intermixing plate.

FIG. 2 (2 a-2 c) shows a step of a production process according to theprior art.

FIG. 3 (3 a, 3 b) shows a functional comparison between the prior artand the invention.

FIG. 4 (4 a-4 d) shows assembling steps according to the invention.

FIG. 5 (5 a, 5 b) is a perspective view of a bridging plate.

Now, the invention will be explained by means of FIGS. 4 and 5, with theprior art shown in FIGS. 1 to 3 included.

FIG. 1 shows a battery case 1 with a lead electrode 2 and a filling ofacid 3, the level of which being denoted by mark 4, when the battery isin the state of rest. The angle-shaped intermixing device comprises avertical leg 5 a and a horizontal leg 5 b. For example, when such abattery is installed in car and the car moving in a direction indicatedby an arrow A is decelerated, the acid between the vertical leg 5 a andthe side wall of battery case is pushed upwardly and drains along thehorizontal leg 5 b. As this procedure takes place repeatedly,intermixing of acid is gained as wanted. In FIG. 1, the intermixingdevice is represented at one side of battery case 1 only.

FIG. 2 shows steps of manufacturing of such a conventional battery. Atfirst, the set of lead electrodes 2 is inserted into the empty batterycase 1. With this procedure, there is the possibility that the set ofelectrodes is not positioned centrally, as shown in FIG. 2 b. The nextstep is to insert one angle-shaped intermixing plate 5 a, 5 b each atboth sides of battery case, as shown in FIG. 2 c. As the set ofelectrodes 2 is positioned too close to the left side wall of battery,there is the possibility that the jackets made of plastic material andprotecting the electrodes are damaged. Such a damage will inevitablylead to a premature breakdown of the respective battery cell and thebattery as a whole.

FIG. 3 a shows schematically another disadvantage of a conventionalproduction method. When the set of electrodes is not exactly positioned,the two flow channels, each of which being formed between the respectiveside wall and the vertical leg of the respective angle-shapedintermixing plate, are different in depth. However, as the flow channelsare optimized with regard to the depth, any change of depth will lead toa reduction of efficiency of intermixing. As shown in FIG. 3 b, theleft-sided flow channel and the right-sided flow channel are equal indepth so that an efficient intermixing takes place, indicated by arrows.

FIG. 4 shows schematically steps of the production method according tothe invention. A novel intermixing device is used here, which iscomposed of three elements, i.e. two intermixing plates 5 a′ and abridging plate 5 b′. At first, the two intermixing plates 5 a′ areinserted into the battery case 1 under a small angle (FIG. 4 b).Thereafter, the set of electrodes 2 is inserted (FIG. 4 c). This enablesthe set of electrodes 2 to be positioned centrally in the battery case1. In the final step represented in FIG. 4 d, the bridging plate 5 isplaced onto the intermixing plates being straightened out vertically andis connected with them at right angles.

FIGS. 5 a and 5 b show perspective views of the two intermixing plates 5a′ and the bridging plate 5 b′, wherein FIG. 5 a is a explosive andperspective view of the intermixing device and FIG. 5 b is a perspectiveview of the assembled intermixing device. It must be emphasized that theinventive method is also suited for making electrolytic batteriesequipped with an intermixing device different in shape from that shownin the figures, as it is the case with batteries used in trucks.

1. Method for making a lead-acid battery having an intermixing device,wherein the method comprises the following steps: inserting ofintermixing plates (5 a′) into the battery case (1), one each at twosides thereof which are opposite to each other, wherein the intermixingplates are positioned slightly inclined, inserting of a set ofelectrodes (2) between the two intermixing plates (5 a′) positioned inthe battery case (1), which thereby are straightened out vertically,wherein the battery case (1), the set of electrodes (2) and theintermixing plates (5 a′) are dimensioned so that the set of electrodesis moved to a constructively predetermined position and thus, flowchannels having a predetermined cross section are formed, and connectingof the two intermixing plates 5 a′ straightened out vertically with thebridging plate 5 b′ comprising a drain surface slightly inclined towardsthe center thereof and an opening provided approximately in the centerthereof to enable electrolyte to flow back into the batter case. 2.Method according to claim 1, characterized in that the bridging plate (5b′) is connected with the two intermixing plates (5 a′) by means ofplug-in elements or clips.
 3. Method according to claim 1, characterizedin that the battery case is supported by a small-roller conveyor whenthe set of electrode (2) is inserted.